A Christian who accepts Islam and then apostatizes

Ibn Ubayd bin al-Abras says that a man was brought to Sayyiduna Ali bin Abi Talib (may Allah be pleased with him) who had been a Christian, then accepted Islam, and then returned to Christianity. The narrator says: He asked him about that matter, and he told him. So Sayyiduna Ali (may Allah be pleased with him) stood up towards him and kicked him with his foot; then the people also stood up and began striking him until they killed him.

Sayyiduna Abu al-Tufayl (may Allah be pleased with him) says: I was in the army that Sayyiduna Ali bin Abi Talib (may Allah be pleased with him) sent to Banu Najiyah. He says: We reached them and found them to be in three groups. Our commander asked one group among them: "What is your situation?" They said: "We were Christians; we did not consider any religion better than our own, so we remained firm upon it." The commander said: "Stand apart." Then he asked a second group: "What is your situation?" They said: "We were Christians, then we accepted Islam, and we remained firm upon Islam." The commander said: "You also stand apart." Then the commander asked the third group: "What is your situation?" They said: "We were Christians, then we accepted Islam, then we turned back. We did not consider any religion better than our first religion, so we took up Christianity." The commander said to them: "Accept Islam." They refused, so the commander said to his companions: "When I pass my hand over my head three times, attack them." They did so, killing those who fought and taking their children captive.

Tawus says that Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: "The Jews and the Christians shall not live in one place with you unless they accept Islam. Whoever among them accepts Islam and then apostatizes, strike nothing but his neck."